. >> reporter: vice president joe biden is in the battleground state of north carolina today while president obama studies for the debate in nevada. he is holding practice sessions with former presidential candidate john kerry, playing the part of mitt romney. on monday, the president called campaign volunteers and told one of them what debate preparation is like. >> basically, they're keeping me indoors all the time. it's a drag. [ laughter ] >> they're making me do my homework. >> reporter: the stakes are high for the debate but both the white house and the romney campaign are trying to lower expectations. neither side wants their candidate to take the stage with a perceived advantage. the polls show most americans believe obama will win the first debate. >> thank you so much. >> reporter: but historically it's the challenger who usually gets a boost. >> less important than what they say is how they appear. do they treat their rival with respect? do they connect with the audience? do they respond at the moment when they have to react? how do they look? how do they seem? >> reporter: the de